Tramaine Brock and Shareece Wright are the projected starters, but how will things shake out after them? Or how will the 49ers line up in nickel defense?

The preseason will help coach Jim Tomsula and his staff determine that and Tomsula called the secondary one of the key areas he wants to keep tabs on in Saturday s exhibition opener in Houston.

Brock, who missed all but three games last season with various injuries, has his focus on winning not one, but a pair of jobs.

My mind set is on No. 1 corner, and I m trying to win the nickel job too, Brock said.

Brock had a strong 2013 season with a team-leading five interceptions, despite starting just seven of the 16 games. He injured his toe in Week 1 last year and that later caused hamstring problems that he wasn t fully recovered from until he reported for training camp.

Brock is well-positioned to be a starter, so why is he also pushing to play nickel?

I always wanted to play it, but the defensive coordinators in the past, they didn t want me in the spot, Brock said. Now, they ve given me the opportunity to play it.

Brock said playing the nickel, a position that defends the slot when teams go to three or more receivers, allows him to be more aggressive and give him opportunities to blitz.

Tomsula said Brock s foot quickness makes him capable of handling that role.

He s a good athlete, he can run, but he can change direction. He can plant and drive, Tomsula said. You start looking at some of those slot positions, those are those little jitterbug dudes. He s bright, he gets it, and he s a competitive son of a gun.

Tomsula isn t sure yet how much nickel Brock will play, but the mere fact he s pushing for that job says something. How many starting corners come to you and say, Hey, give me a shot at that nickel , Tomsula said. They want to stay out there and do their thing. He s coming and saying, Hey, I want to do that job. Give me a chance.

Brock s main competition at nickel would be 2014 first-round pick Jimmie Ward, but Ward hasn t participated in team drills yet as he continues to recover from last year s foot injury. He won t travel to Houston for Saturday s game, but Tomsula said he s making good progress.

You ve seen him out there in individuals, see him moving, Tomsula said of Ward. You re not seeing any hitch in the giddy up.

Dontae Johnson and Keith Reaser, two more pieces from the 2014 draft, will be in the mix to slide in at cornerback if Brock plays nickel and are players that can give the 49ers some good young depth.

If all goes well with them, there s a chance to 2014 draft could up delivering a major haul of secondary playing time. Kenneth Acker, in the mix to back up Wright at right cornerback, is another 2014 draftee.

They could end up pushing out last year s midseason free agent pickups, Marcus Cromartie and Leon McFadden. After the 49ers released veteran Chris Cook this offseason, it sent a message to the younger players.

It tells you they re definitely looking for younger guys to step up and be part of the defense, said Reaser, who missed all of his rookie season recovering from two surgeries on his torn anterior cruciate ligament. Also it tells you too that if I m not getting it done or whatever, I could be gone as well.